The basic concept of the asphalt or concrete road paver system has remained relatively unchanged for many years. Screed plate assemblies for paving are found and utilized in various construction paving industrial settings, such as pavement of highways, airports, streets and other sites requiring paving of constructional site beds and pads, requiring a paving mat. Paving materials, such as concrete or hot mix asphalt (HMA), is loaded in the front of the road paving tractor, typically in a hopper, and conveyed to the rear by a set of flight feeders (conveyor belts), where it is spread out to a desired width by a set of augers in the road paver, and then leveled and compacted by a screed plate. The most critical feature of a road paver is the self-leveling, or free floating, screed unit or assembly which will determine the quality or profile of the material being paved or placed on the road bed at the correct mat smoothness and thickness. The free floating screed assembly slides across the material. The screed plate is the flat bottom portion of the screed assembly that flattens and compresses the material into the mat. Screed heaters or heating elements, such as gas and electric heating elements, are used to preheat the screed so that the material does not stick to the screed plate and cause mat tearing.
There has been in the road paving industry a recognized need for changing worn screed plates to a road paving machine. Flexibility and ease of changing screed plate assemblies is found to be extremely beneficial in construction paving operations. Dealing with loss of operation time, increased costs and operational restrictions and limitation of current screed plates are major concerns for paving operations.
The conventional screed plate assembly is constructed of a one piece metal alloy screed plate. Screed plate replacement, particularly on site, is difficult, time consuming and laborious. Screed plates during paving do not wear evenly. The wear on the screed plates typically occurs in isolated spots on the plate. There needs to be an assembly, system or device whereby lower wear areas of the screed plate may be rotated to higher wear areas, or higher wear areas need to be replaced while leaving lower wear areas in place.
In the conventional technology used today, the paving machine provides an electrically or gas heated screed assembly with heating elements attached to or adjacent to a screed plate. This conventional screed plate assembly provides for one screed plate underlying the paving machine. There is no known technology being used to solve the problem of screed plate wear maintenance that does not include removing the entire screed, and the structural plate adjacent to the heating element of the paving machine. Removal of the plate in conventional screed plate assemblies requires, in most cases, disassembly of the heating system as well as the plate. As well, there has been no device to solve the problem of the uneven wear experienced by conventional screed plate assemblies.
Finally, there is a need to be able to utilize different screed plate materials for differing applications. The conventional structural/conductor plate is a single plate made of steel, required in part due to its direct contact with the heating system. A separate structural/conductor plate providing for intervening, direct contact with the heating system would allow for the use of alternative materials for the screed plates. Alternative materials, such as nickel, copper, aluminum, steel or metal alloy of copper or nickel (having high conductivity and anti corrosion capabilities), will provide better conductivity and corrosion resistence.
The conventional screed plate is a single plate made of steel, required in part due to the structural requirements of having one piece of plate engaged in paving. Alternative materials, such as cast nickel hardened, or “Ni-hard”, or poly-plastics, and modular plates, will provide longer wear and/or less costly alternatives.
The references described in the related art do not disclose features of the present invention and would not be as suitable for the required purpose of the present invention hereinafter described. Screed plate devices are found in the related art, exemplified by U.S. Pat. No. 6,551,021 to Baker (“Baker”); U.S. Pat. No. 8,517,630 to Graham et al. (“Graham”); and U.S. Pat. No. 9,181,662 to Kopacz et al. (“Kopacz”). Graham discloses the use of upper and lower screed plates with an electric resistive heater disposed between the upper and lower plates to directly heat both plates. The upper plate in Graham remains fixed while the lower plate may be removed and replaced. The upper and lower plates of Graham have different wear and thermal properties. Kopacz discloses a screed electrical heating assembly that is adapted to provide easy replacement, and a similar arrangement to Graham. However, none of the known references disclose or suggest the use of a fixed structural/conductor plate in place of a fixed upper screed plate frame with the heating means disposed to only heat the structural/conductor plate. Graham and Kopacz disclose a heating means provided between the fixed screed plate frame and the lower screed plate which provides direct heating to the screed plate. There is no prior art suggestion for moving the heating means so that it may only heat the upper frame plate which will then provide indirect heat to the screed plate as in the present invention.
Baker discloses a screed plate attaching to a support assembly and having an interlock system comprising tabs and notches that are configured to fit together and secured by a fastener. The tab and slot system in Baker simply prevents non-matching plates from interconnecting. There is no disclosure in any of the references for the tab and slot locking system of the proposed structural/conductor plate to the screed plate as disclosed by the present invention.
None of the references in the prior art contain every feature of the present invention, and none of these references in combination disclose, suggest or teach every feature of the present invention.
The foregoing and other objectives, advantages, aspects, and features of the present invention will be more fully understood and appreciated by those skilled in the art upon consideration of the detailed description of a preferred embodiment, presented below in conjunction with the accompanying drawings.